Electric lamp



Dec. 7 1926.

P. K. DEVERS, JR

EIJECTRIC LAMP Filed June 1, 1923 flvl/eflto/y Ph/W a A. De Mel-s Jr; yMf His fitter-nay.

Patented Dec. 7, 1926.

UNITED STATES PATENT OFFICE.

PHILIP K. DEVERS, JR, 0]? LYNN, MASSACHUSETTS, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC LAMP.

Application filed June 1,

The present invention relates to electric arc lamps and its object is toprovide a lamp of high efiieiency which will emit substan tially whitelight. I

My invention relates particularly to arc lamps in which theelectrodesare adapted to operate at incandescence in a gas or vapor at substantialpressure. Mercury vapor is one of the most convenient and efiicientmedia for the operation of an'arc in a lamp of this character as lightisderived at high efliciency from the arc itselfas'well as from theelectrode but as the light from a mercury arc is deficient inraysadjacent the red end of the spectrum the combined light from theincandescent electrodes and the are become somewhat yellowishgreen incolor when light from the arc. predominates. This condition existsordinarily when the arc is longer than about one-eighth inch.

In accordance with. my invention I have provided a lamp in which thehigh efficiency of the arc is most completely utilized by providing arefractory'body intermediate the electrodes which preferably is' capableof radiating light predominant in color adjacent the red end of thespectrum when heated to incandescence by the arc.

The accompanying drawing illustrates an embodiment of my invention, Fig.1 being a side view and Figs. 2 and 8 somewhat enlarged detail views ofthe support and the electrodes respectively. I

Referring to Fig. 1, the lamp consists of 'an elongated glass receptacle1, preferably having a bulbous enlargement at its lower end. The mainelectrodes 2, 3, preferably consisting of a refractory metal forexample, tungsten, are carried at the end of the conductors 4, 5 whichare sealed into a stem 6 at the 0 posite end of the lamp. The portion ofthese conductors adjacent the electrodes preferably has a reduceddiameter to conserve heat at the electrode. The main electrodes consist,in the device illustrated, of cylinders about .125" in diameter and.090" in length. Adjacent the electrodes is a pool 7 of mercury, or anamalgam of alkali metal or other suitable vaporizable material. The bulbalso preferably contains an inert gas, as for example, argon, neon,'nitro'gen, or-the like, or of a suitable mixture thereof, at a pressureof about a third of an atmosphere. A wire 8 having a loop dipping intothe mercury is connected to the 1923. Serial No.- 642,840.

conductor 5 at one end while the other end is sealed into the stem.\Vhen this wire, which preferably also consists of tungsten, is heatedto incandescence ionized vapor is produced and an arc may be startedbetween the main electrode with greater facility, as described in myprior Patent 1,310,067 of July 15, 1919.

Between the electrodes and in direct heating relation to the arc is arefractory body 10 having about the same size as the elec-' trodes andconsisting of a material which preferably selectively radiates lightnea'rthe red end of the spectrum. Zirconium oxide,

carbide and silicate and thorium 1ox ide are examples of materialssuitable for this pur pose.. This glower 10'is carried by a stein 11,.consisting of tungsten or other suitable refractory material whichisanchored at the opposite end in an insulating support 12 carried by theconductors 4, 5.

When an arcis started as described in my prior patent, mercury isvaporized and as the mercury vapor replaces the fixed gas,

the arc becomes highly luminous. The glo'wer 10 also becomes heated bythe arc, emitting light and becoming electrically conductive. It may besaid to function as a neutral electrode. During operation there arevirtually two distinct arcs in series, as the heated glower which emitselectrons freely does not interfere with the operation of the are, notraise the voltage required 'to maintain a continuous arc of the sametotal length between tungsten electrodes. For instance, a mercury arebetween tungsten electrodes operating normally. would take about 40amperes with a potential drop of about 25 volts and would give, adistinctly yellowish green light. Two mercury arcs in series with thedescribed central electrode would operate with substantiall the sameterminal electrical 'characterlstics.

The combination would emit substantially white light providing theintermediate neutral electrodehad been properly chosen and proportioned.The color characteristic of the lamp is very flexible since by varyingthe lengths of the arcs and the size of the neutral electrode the colorcan be.varied over a wide range.

new and desire to secure I .for supplying mercury vapor to the spacebetween said electrodes and a body consisting of zirconium oxide locatedin the path of an are between said electrodes.

3. An electric lamp comprising electrodes adapted to operate atincandescence, an en-' closing envelope, a gas therein inert withrespect to said electrode at incandescence, a body of mercury adjacentsaid electrodes, means for starting'an are between said electrodes and abody of refractory material located directly in the path of said areintermediate said electrodes, said body having approximately the samesize as said electrodes andbeing capable of radiating light atincandescence predominately near the red end of the spectrum.

In witness whereof, I have hereunto set my hand this 29th day of May,1923.

. .PHILIP K. DEVER-S, JR.

